1. Field of the Invention
The present invention relates to a satellite navigation system comprising a server and on-vehicle navigating terminals communicably connected to the server via a communication network, wherein map data supplied to the navigating terminals are partially updateable.
2. Description of Related Art
In recent years, a satellite navigation system has become popular. The satellite navigation system guides a user (driver) to a user""s desired destination with a map shown on a navigating terminal. A practical configuration of such satellite navigation system is configured as now described. In response to a user""s request, map data stored in a server placed at a map data base site are transmitted to such a navigating terminal as an on-vehicle navigation unit, mobile navigation unit, PDA (personal digital assistants), or mobile phone, through communication means. The communication means is composed of for example a computer network (e.g., the Internet) or a mobile communication network. The navigating terminal includes a GPS (global-positioning system) to detect a vehicle""s current position, and provides a map on a monitor thereof using both the vehicle""s current position and the received map data.
Such a satellite navigation system is advantageous in that it is able to enable each navigating terminal (i.e., a user) to make reference to the newest versions of maps. In order to gain the advantage, a user has to have the newest map data by reloading map data stored in a memory block in the navigating terminal, whatever the map data handled in the server is updated.
On the other hand, in each navigating terminal participating in the satellite navigation system, a unit of map data accumulated in the navigating terminal is marked, area by area, by points to relate them to each other.
However, in the conventional satellite navigation system, it is difficult to alter or modify only partial map data (for example, only data of a background or a road) when the map data is updated, because the unit of map data is marked area by area by points. Even when some notes (for example, characters or symbols) are update alone, the entire unit of the map data must be reloaded. Accordingly, processing to replace the old map data with new one is required in the navigating terminal. Thus, amounts of data to be reloaded become extremely large, resulting in a longer time for data processing in the reloading and a higher cost of the reloading.
To make matters worse, this reloading might have influence on the surrounding unit coupled with the map data unit or superior or inferior units to the map data unit. Such a case becomes an obstacle to smooth and steady operations for navigation.
The present invention has been made in view of the above circumstances. An object of the present invention is, therefore, to greatly reduce an amount of data to be re-loaded when map data is updated.
The present invention is reduced into practice in various aspects, such as a server incorporated in a satellite navigation system and a method of updating map data in the satellite navigation system.
In order to achieve the above object, as one aspect of the present invention, there is provided a method of updating map data in a satellite navigation system comprising a server storing map data to be displayed on a terminal; the method comprising the steps of: producing the map data divided into a plurality of sets of map data that are mutually-independent set by set, the divided map data being stored in the server; and updating, every set of the divided map data, the map data stored in the server.
As a result, in the server, the map data can be replaceable partially, that is, every set of divided data map, in an easier manner. This partially replaceable configuration is also effective in reloading map data from the server to each navigating terminal. For reloading the map data, it is sufficient that only one or more sets of map data that has been updated are delivered from the server to the navigating terminal. Hence an amount of map data to be downloaded can be reduced greatly.
Further, because the map data are divided into a plurality of sets independent of each other, each certain set of map data can be replaceable with no effect on the other sets of map data in terms of data connections.
Preferably, the updating step is one selected from a group of processes including a step of adding a new set of map data to the map data, a step of deleting a certain set of map data from the plurality of sets of map data, and a step of replacing a certain set of map data of the plurality of sets of map data with a new set of map data. By way of example, the map data consists of different kinds of map data formed into a layered structure of map data.
It is also preferred that the layered structure of map data includes a first layer formed by data of a plurality of objects, a second layer formed by a plurality of blocks, each block consisting of one or more objects of the same kind, and a third layer formed by a plurality of layers, each layer consisting of data of a plurality of blocks for the same type of depiction of map data. By way of example, each set of the map data is composed of one of each layer of map data, each block of map data, and each object of map data.
In order to accomplish the foregoing object, as another aspect of the present invention, there is provided a server for storing map data to be displayed on a terminal, both of the server and the terminal being incorporated in a satellite navigation system, the server comprising: a storage for storing the map data divided into a plurality of sets of map data that are mutually-independent set by set, the divided map data being stored in the server; and an updating unit configured to update, every set of the divided map data, the map data stored in the server.
Accordingly, this configuration also provides the same advantages as those explained above. That is, because the map data can be replaceable partially in the server, it is sufficient that only one or more sets of map data that has been updated are delivered from the server to the navigating terminal in reloading the map data. Hence an amount of map data to be downloaded can be reduced greatly. Further, the map data are divided into a plurality of sets independent of each other, so that each certain set of map data can be replaceable with no affection for the other sets of map data in terms of data connections.
In the above second configuration, it is preferred that wherein the updating unit is configured to perform one selected from a group of processes including adding a new set of map data to the map data, deleting a certain set of map data from the plurality of sets of map data, and replacing a certain set of map data of the plurality of sets of map data with a new set of map data. By way of example, the map data consists of different kinds of map data formed into a layered structure of map data.
It is also preferred that the layered structure of map data includes a first layer formed by data of a plurality of objects, a second layer formed by a plurality of blocks, each block consisting of one or more objects of the same kind, and a third layer formed by a plurality of layers, each layer consisting of data of a plurality of blocks for the same type of depiction of map data. Preferably, each set of the map data is composed of one of each layer of map data, each block of map data, and each object of map data.
According to another aspect of the present invention, there is provided a recording medium for storing map data, which is incorporated in a server of a satellite navigation system, the map data being divided into a plurality of sets of map data that are mutually-independent set by set, updateable every set of the divided map data, and configured to have different kinds of map data formed into a layered structure of map data, wherein the layered structure of map data includes a first layer formed by data of a plurality of objects, a second layer formed by a plurality of blocks, each block consisting of one or more objects of the same kind, and a third layer formed by a plurality of layers, each layer consisting of data of a plurality of blocks for the same type of depiction of map data.